Respiratory tract disease is a major cause of morbidity and mortality worldwide. A variety of pathogens have been identified that cause upper and lower tract disease yet the etiology of a significant proportion of respiratory disease remains unclear. The Human Metapneumovirus (HMPV) is a newly discovered pathogen that has been reported from the Netherlands, Australia and Canada. Our preliminary results demonstrate that HMPV is circulating in New Haven, CT. Little is known about clinical characteristics of this new pathogen, it appears to cause both upper and lower respiratory disease. Using RT-PCR we have been able to identify HMPV genomic sequences from respiratory samples. We intend to enhance the RT-PCR sensitivity by creating primers that correspond to conserved regions of the genome. We will develop an immunofluorescence screen based on production of HMPV antibodies in experimental animals. These antibodies will be generated by immunizing experimental animals with recombinant HMPV F and synthetic peptides corresponding to conserved regions of the HMPV F gene. Growth, propagation and cytopathic effects on LLC-MK2 cells will also be utilized. All respiratory samples received by the Clinical Virology Laboratory will then be screened for the presence of HMPV. We will study the seasonal distribution, and attempt to identify populations at risk. The medical records of patients identified with HMPV will then be reviewed to establish the clinical characteristics. The seroprevalence will be defined using ELISA techniques to screen for the presence of anti-HMPV antibody.